This invention relates to a method and an apparatus for checking syringe bodies, where by “syringe body” is meant at least the main portion of a syringe containing the liquid product to be injected, that is to say, the cylindrical body of glass or plastic and the rear sliding seal (known as “plunger” in technical jargon) of rubber, defining a fluid seal with the inside surface of the cylindrical body. Further, the invention applies in particular to checking syringes of the ready-to-use, single dose type, containing a dose of liquid ready for injection.
The syringe bodies, usually without the needle and the plunger rod (the part acted upon by the user and coupled to the plunger or seal) are normally tested before going to market in order to check their fluid tightness to guarantee they are leakproof.
To do this, the syringe bodies are placed in an atmosphere under negative pressure allowing any leakage sites to be detected.
This operation exposes the entire outside surface of the syringe body to the pneumatic negative pressure and this may cause the rubber seal or plunger to withdraw towards the rear end of the cylindrical body. Under certain conditions, this withdrawal may cause the seal and/or the liquid to come into contact with parts of the syringe body which are not sterile, resulting in contamination and making the product permanently unfit for use.